1. Field of the Invention
The present invention relates to a sector pulse generating technique in a hard disk drive, it and more particularly, to a sector pulse generating technique using a defect swallowing method therein.
2. Description of the Related Art
In general, a hard disk drive should be free from defects which may be generated due to a poor material, during manufacturing, or upon delivering a product. In fact, since most customers want to buy a defect-free drive, it is necessarily required to effectively eliminate the effects of generated defects without having any adverse effects on a the performance of the drive and accordingly, such elimination techniques have become a key concern to a manufacturers.
Moreover, as media recording technique are rapidly being developed, a real recording density has increased in proportion thereto. Therefore, a negligible defect which could be disregarded in the conventional system now has now a serious adverse effect. Accordingly, a more perfect medium is required and due to this, the product cost is inevitably increased. In order to overcome these disadvantages, various error correction methods using an ECC logic of a drive controller and a defect removing method using software processing have arisen.
The EEC correction method utilizes hardware which includes a plurality of disks rotated by a spindle motor driver. The disks have support arms extending from an E-block assembly connected to a VCM driver and disposed towards the disks. A preamplifier preamplifies the signal which is picked up by one of the heads at the time of reading so as to supply an analog read signal to a read/write channel circuit. The preamplifier writes encoded write data supplied from the read/write channel circuit onto the disk through one corresponding head at the time of writing. The read/write channel circuit detects a data pulse from the read signal supplied from the preamplifier and alternatively decodes the detected data pulse and supplies the decoded data pulse to the preamplifier. A DDC writes data received from a host computer onto the disk through the read/write channel circuit and the preamplifier. The DDC interfaces a communication between a host computer and a CPU. Data transmitted between the host computer, the CPU and the read/write channel circuit is temporarily stored in a buffer RAM. The CPU controls the DDC in response to a read/write command received from the host computer and controls a track seek and a track follow. All of the established values and an execution program of the CPU are stored in a ROM. The CPU drives the S/M driver to rotate the disks in accordance with a control value for controlling the rotation of the disks, the control value being generated by the CPU. A disk signal control generates all timing signals necessary for the read/write operation under the control of the CPU and decodes the servo information and supplies the decoded servo information to the CPU. And ECCOTF (ECC on the fly) method which simultaneously processes errors of an entire sector while reading data of a next sector by hardware has been used. Recently, concern has been focused on a manner of effectively expanding the ECC correction span. Furthermore, a Reed Solomon S/W ECC method capable of processing errors using software has been used, through it is less effective than the ECCOTF method. However, if a defective sector cannot be corrected through the above two methods, a method has been used of skipping a defective sector and then reading the other non-defective sectors. In this case, it seems to a user as if the disk operates normally. If general, a method of removing defects, as mentioned above, includes a defect skipping method and a defect moving (vectoring) method. The defect skipping method, which uses several spare sectors in a unit of a track or a cylinder, upon the generation of a defect, moves a generated defect to a sector just next to the defective sector. The defect moving, which moves the generated defect to a maintenance cylinder or to another defect-free location, is used in a situation when spare sectors are all used, or, in drives employing the spare sector scheme.
In case of using these methods, although a defect occurs on only part of one sector (1-7 bytes), the entire sector (512 bytes) must be discarded. One sector includes an ID field, a sync and a dummy pad field, etc., and has capacity of about 570 bytes and spare areas for the defect should previously be prepared in a given part of the drive, thereby increasing a capacity loss in the drive. Furthermore, since data of the defective sector has to be repaired, data must be read from another location. In the defect skipping method, a time delay corresponding to one sector is generated, but, in the defect moving method, a seek time and a latency time are required and accordingly, the performance is substantially reduced. On the other hand, with a defect swallowing method, only the defective part is skipped and the remaining non-defective parts are used and as a result, this method can relatively reduce the capacity loss and does not need much spare areas.
The Golden, et al. patent, U.S. Pat. No. 5,367,652 entitled DISC DRIVE TRANSLATION AND DEFECT MANAGEMENT APPARATUS AND METHOD, discloses a disk drive translation and defect management technique in which a controller having an index table and a defect table is used to offset a value of the location of a defect, the location being stored in the defect table.
The following patents each disclose features in common with the present invention but do not teach or suggest the specifically recited features thereof:
U.S. Pat. No. 5,506,735 issued to Okazaki entitled Magnetic Disk Drive Having Programmable Sector Pulse Generator And Processor Determined Track Zones. PA1 U.S. Pat. No. 5,276,564 issued to Hessing, et al. entitled Programmable Start-Of-Sector Pulse Generator For A Disk Drive Using Embedded Servo Bursts And Split Data Fields. PA1 U.S. Pat. No. 5,271,018 issued to Chan entitled Method And Apparatus For Media Defect Management And Media Addressing. PA1 U.S. Pat. No. 5,068,755 issued to Hamilton, et al entitled Sector Pulse Generator For Hard Disk Drive Assembly. PA1 U.S. Pat. No. 4,746,998 issued to Robinson, et al. entitled Method For Mapping Around Defective Sectors In A Disc Drive.